feat(pos): migrate CFDI timbrado from Horux to Facturapi

- Add Facturapi REST service (invoices, customers, orgs, cancel, downloads)
- Add JSON payload builder for ingreso/egreso/pago/global invoices
- Replace XML queue with Facturapi JSON queue (payload_unsigned, external_id)
- Update invoicing blueprint with Facturapi config and download endpoints
- Update global invoice service to use Facturapi payloads
- Add migration v4.3_facturapi.sql and tenant rollout script
- Update invoicing UI: payload preview, PDF/XML downloads, PAC status panel
- Add FACTURAPI_USER_KEY to .env.example

pos/services/global_invoice.py

@@ -8,7 +8,7 @@ monthly CFDI with InformacionGlobal per SAT requirements.
 from datetime import datetime
 from decimal import Decimal
 
-from services.cfdi_builder import build_global_invoice_xml
+from services.cfdi_facturapi_builder import build_global_invoice_payload
 from services.cfdi_queue import enqueue_cfdi, _generate_provisional_folio
 
 
@@ -137,10 +137,10 @@ def generate_global_invoice(conn, tenant_config, year, month, branch_id=None,
         return {'error': 'NO_ELIGIBLE_SALES',
                 'message': f'No hay ventas elegibles para factura global de {month:02d}/{year}'}
 
-    xml = build_global_invoice_xml(sales, tenant_config, year, month)
+    payload = build_global_invoice_payload(sales, tenant_config, year, month)
 
     # Enqueue with sale_id=NULL (global invoice)
-    result = enqueue_cfdi(conn, None, 'ingreso', xml)
+    result = enqueue_cfdi(conn, None, 'ingreso', payload)
     cfdi_id = result['id']
 
     cur = conn.cursor()
@@ -167,7 +167,7 @@ def generate_global_invoice(conn, tenant_config, year, month, branch_id=None,
         'sales_count': len(sales),
         'total': sum(s['total'] for s in sales),
         'provisional_folio': result['provisional_folio'],
-        'xml': xml,
+        'payload': payload,
     }